Apparatuses for recording or reproducing information or data in one or more tracks of a recording medium which are provided with a scanning device, referred to as a “pick-up”, for reading or recording the information are known. The respective scanning device is usually arranged on a carriage which can be made to move obliquely or perpendicularly in relation to the respective recording track of the recording medium and, by being electromotively driven, said carriage can be made to move at high speed and with great positioning accuracy, combined with a short access time to different locations of the recording medium.
The optical scanning devices comprise in a known way a series of optical components for directing and aligning a laser beam on the path to the respective recording medium and from the latter to a detector, such as gratings, beam splitters, a collimator, deflecting mirrors, quarter-wave plates and lenses, which must be arranged very precisely in relation to one another to allow the respective recording medium to be illuminated positionally accurately and its data to be transmitted accurately to an optical detector. Since all the optical components and mechanical parts have specific production and assembly tolerances, some components must be adjustable before they are securely arranged, in particular by adhesive bonding, on the scanning device. These generally include a number of optical gratings, the collimator and a focusing lens.
Only a small space is available for arranging or actuating the required holding devices and adjusting tools, since the dimensions of the optical drives including the scanning device are minimized in particular to meet computer standards, so that the holding devices and adjusting tools must be designed correspondingly.
The subject matter of JP 01-096612 is a mounting device, serving at the same time as an adjusting device, for a lens fixed in a cylindrical lens holder by an adhesive bond. In the case of this adjusting device, the lens holder is arranged in a base block with a cylindrical receptacle and is adjustable about and along its optical axis. Two setting screws, which are arranged on the base block, are in operative connection with a flank arranged on the lens holder tangentially in relation to the optical axis and the actuation of which brings about a clockwise or counterclockwise rotation of the lens holder, serve for the adjustment about the optical axis. For the adjustment in the axial direction, provided on the base block is a setting screw with an eccentrically arranged pin, which is in engagement with a coaxial circumferential groove, arranged on the lens holder, and the rotation of which brings about a displacement of the lens holder in the axial direction. Consequently, a number of setting elements or individual devices are required and have to be actuated for the adjustment of the lens in the direction of the optical axis and about the optical axis.
Furthermore, it is known to mount an optical component in a prismatic mounting part with two surfaces arranged substantially at right angles to each other, which is made to bear with a leaf spring against two reference surfaces of a base part of the scanning device, a so-called optic body, which are aligned parallel to the optical axis. This mounting part can be displaced with an eccentric setting element along the reference surfaces, and consequently along the optical axis. The engagement for an adjusting tool is in this case provided via an opening in the bottom of the base part.
It is also known to arrange a cylindrical mounting part, in which an optical component is adhesively embedded, with a leaf spring on two reference surfaces aligned parallel to the optical axis and arranged substantially at right angles to each other, in such a way that the mounting part is provided with an eccentric setting element which can be displaced along the optical axis, by an adjusting tool which can be brought into engagement with said setting element via an opening in the base part and can be rotated about the optical axis by a further setting element for a corresponding adjusting tool.
The known arrangements described above require not only corresponding setting elements to avoid a “stick-slip effect” and to ensure a smooth setting movement of the respective mounting part during the adjustment, but also a relatively great freedom of movement for the respective adjusting tool. If a possibility of adjusting the optical element about the optical axis is additionally required, an adjusting tool designed for this movement is necessary, so that possibly two setting operations with two different adjusting tools have to be carried out for an adjustment of the optical element. Moreover, there are limits to the accuracy of the respective setting movement, so that a predetermined desired position of the optical element may require a number of corrective adjustments.